Multifunctional olefin copolymer and lubricating oil composition

ABSTRACT

An additive composition comprising a graft and derivatized copolymer prepared from ethylene and at least one C 3  -C 10  alpha-monoolefin and, optionally, a polyene selected from non-conjugated dienes and trienes comprising from about 15 to 80 mole percent of ethylene, from about 20 to 85 mole percent of said C 3  -C 10  alpha-monoolefin and from about 0 to 15 mole percent of said polyene having an average molecular weight ranging from about 5,000 to 500,000, which has been reacted with at least one olefinic carboxylic acid acylating agent to form one or more acylating reaction intermediates characterized by having a carboxylic acid acylating function within their structure and reacting said reaction intermediate with an amino alkylthio thiadiazole to form said graft derivatized copolymer, and a lubricating oil composition containing same are provided.

BACKGROUND OF THE INVENTION

This invention relates to a novel multifunctional lubricant additivewhich is a VI improver, a dispersant, an antiwear agent, and anantioxidant additive when employed in a lubricating oil composition.

DISCLOSURE STATEMENT

The art contains many disclosures on the use of polymer additives inlubricating oil compositions. Ethylene-propylene copolymers andethylene-alpha olefin non-conjugated diene terpolymers which have beenfurther derivatized to provide multifunctional properties in lubricatingoil compositions illustrate this type of oil additive.

U.S. Pat. No. 4,089,794 discloses ethylene copolymers derived fromethylene and one or more C₃ -C₂₈ alpha-olefins grafted with anethylenically unsaturated carboxylic acid material followed by areaction with a polyfunctional material reactive with carboxyl groups,such as a polyamine, a polyol, or a hydroxyamine which reaction productis useful as a sludge and varnish control additive in lubricating oils.

U.S. Pat. No. 4,137,185 discloses a stabilized imide graft of anethylene copolymer additive for lubricants.

U.S. Pat. No. 4,146,489 discloses a graft copolymer where the backbonepolymer is an oil-soluble ethylene-propylene copolymer or anethylene-propylene-diene modified terpolymer with a graft monomer ofN-vinyl-pyridine or N-vinylpyrrolidone to provide a dispersant VIimprover for lubricating oils.

U.S. Pat. No. 4,320,019 discloses a multipurpose lubricating additiveprepared by the reaction of an interpolymer of ethylene and a C₃ -C₈alpha-monoolefin with an olefinic carboxylic acid acylating agent toform an acylating reaction intermediate which is then reacted with anamine.

U.S. Pat. No. 4,340,689 discloses a process for grafting a functionalorganic group onto an ethylene copolymer or an ethylene-propylene-dieneterpolymer.

U.S. Pat. No. 4,357,250 discloses a reaction product of a copolymer andan olefin carboxylic acid via the "ene" reaction followed by a reactionwith a monoamine-polyamine mixture.

U.S. Pat. No. 4,382,007 discloses a dispersant-VI improver prepared byreacting a polyamine-derived dispersant with an oxidizedethylene-propylene polymer or an ethylene-propylene diene terpolymer.

U.S. Pat. No. 4,144,181 discloses polymer additives for fuels andlubricants comprising a grafted ethylene copolymer reacted with apolyamine, polyol or hydroxyamine and finally reacted with an alkarylsulfonic acid.

The disclosures in the foregoing patents which relate to VI improversand dispersants for lubricating oils; namely, U.S. Pat. Nos. 4,089,794,4,137,185, 4,144,181, 4,146,489, 4,320,019, 4,340,689, 4,357,250, and4,382,007 are incorporated herein by reference.

An object of this invention is to provide a novel derivatized graftcopolymer composition.

Another object of the invention is to provide a multifunctionallubricant additive effective for imparting viscosity index, dispersancy,antiwear and antioxidant properties to a lubricating oil composition.

A further object is to provide a novel lubricating oil compositioncontaining the graft copolymer additive of the invention, as well as toprovide concentrates of the novel additive of invention.

SUMMARY OF THE INVENTION

The novel reaction product of the invention comprises a polymer,copolymer or terpolymer of a C₃ -C₁₀ alpha-monoolefin and, optionally, anon-conjugated diene or triene on which has been grafted anethylenically unsaturated carboxylic function which is then furtherderivatized with an amino alkylthio thiadiazole represented by theformula: ##STR1## in which R is --NH₂, --CH₂ --(CH₂)_(n) --NH₂,

--CH₂ --aryl--NH₂ in which n has a value from 1 to 10, and

R' is hydrogen, a hydrocarbyl radical having from 1 to 10 carbon atoms,or a hydroxyalkyl or alkoxyl radical having from 2 to 10 carbon atoms.

The novel lubricant of the invention comprises an oil of lubricatingviscosity and an effective dispersant, viscosity index improving,antiwear and antioxidant amount of the novel reaction product of theinvention.

Concentrates of the reaction product of the invention are alsocontemplated.

DETAILED DESCRIPTION OF THE INVENTION

The polymer or copolymer substrate employed in the novel additive of theinvention may be prepared from ethylene and propylene or it may beprepared from ethylene and a higher olefin within the range of C₃ -C₁₀alpha-monoolefins.

More complex polymer substrates, often designated as interpolymers, maybe prepared using a third component. The third component generally usedto prepare an interpolymer substrate is a polyene monomer selected fromnon-conjugated dienes and trienes. The non-conjugated diene component isone having from 5 to 14 carbon atoms in the chain. Preferably, the dienemonomer is characterized by the presence of a vinyl group in itsstructure and can include cyclic and bicyclo compounds. Representativedienes include 1,4-hexadiene, 1,4-cyclohexadiene, dicyclopentadiene,5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 1,5-heptadiene, and1,6-octadiene. A mixture of more than one diene can be used in thepreparation of the interpolymer. A preferred non-conjugated diene forpreparing a terpolymer or interpolymer substrate is 1,4-hexadiene.

The triene component will have at least two non-conjugated double bonds,and up to about 30 carbon atoms in the chain. Typical trienes useful inpreparing the interpolymer of the invention are1-isopropylidene-3α,4,7,7a-tetrahydroindene,1-isopropylidenedicyclopentadiene,dehydro-isodicyclopentadiene, and2-(2-methylene-4-methyl-3-pentenyl)[2.2.1]bicyclo-5-heptene.

The polymerization reaction to form the polymer substrate may be carriedout in the presence of a catalyst in a solvent medium. Thepolymerization solvent may be any suitable inert organic solvent that isliquid under reaction conditions for solution polymerization ofmonoolefins which is generally conducted in the presence of a Zieglertype catalyst. Examples of satisfactory hydrocarbon solvents includestraight chain paraffins having from 5 to 8 carbon atoms, with hexanebeing preferred. Aromatic hydrocarbons, preferably aromatic hydrocarbonshaving a single benzene nucleus such as benzene, toluene and the like;and saturated cyclic hydrocarbons having boiling point rangesapproximating those of the straight chain paraffinic hydrocarbons andaromatic hydrocarbons described above, are particularly suitable. Thesolvent selected may be a mixture of one or more of the foregoinghydrocarbons or a suitable oil base stock. It is desirable that thesolvent be free of substances that will interfere with a Zieglerpolymerization reaction.

In a typical preparation of a polymer substrate, hexane is firstintroduced into a reactor and the temperature in the reactor is raisedmoderately to about 30° C. Dry propylene is fed to the reactor until thepressure reaches about 40-45 inches of mercury. The pressure is thenincreased to about 60 inches of mercury and dry ethylene and5-ethylidene-2-norbornene are fed to the reactor. The monomer feeds arestopped and a mixture of aluminum sesquichloride and vanadiumoxytrichloride are added to initiate the polymerization reaction.Completion of the polymerization reaction is evidenced by a drop in thepressure in the reactor.

Ethylene-propylene or higher alpha-monoolefin copolymers may consist offrom about 15 to 80 mole percent ethylene and from about 20 to 85 molepercent propylene or higher monoolefin with the preferred mole ratiosbeing from about 25 to 75 mole percent ethylene and from about 25 to 75mole percent of a C₃ -C₁₀ alpha monoolefin with the most preferredproportions being from 25 to 55 mole percent ethylene and 45 to 75 molepercent propylene.

Terpolymer variations of the foregoing polymers may contain from about0.1 to 10 mole percent of a non-conjugated diene or triene.

The polymer substrate, that is, the ethylene copolymer or terpolymer, isan oil-soluble, substantially linear, rubbery material broadly having anumber average molecular weight from about 5,000 to 500,000, with apreferred molecular weight range of 25,000 to 250,000, and a mostpreferred range being from 50,000 to 150,000.

The terms polymer and copolymer are used generically to encompassethylene copolymers, terpolymers or interpolymers. These materials maycontain minor amounts of other olefinic monomers so long as their basiccharacteristics are not materially changed.

An ethylenically unsaturated carboxylic acid material is next graftedonto the prescribed polymer backbone. These materials which are attachedto the polymer contain at least one ethylenic bond and at least one,preferably two, carboxylic acid or its anhydride groups or a polar groupwhich is convertible into said carboxyl groups by oxidation orhydrolysis. Maleic anhydride or a derivative thereof is preferred. Itgrafts onto the ethylene copolymer or terpolymer to give two carboxylicacid functionalities. Examples of additional unsaturated carboxylicmaterials include chloromaleic anhydride, itaconic anhydride, or thecorresponding dicarboxylic acids, such as maleic acid, fumaric acid andtheir monoesters.

The ethylenically unsaturated carboxylic acid material may be graftedonto the polymer backbone in a number of ways. It may be grafted ontothe backbone by a thermal process known as the "ene" process or bygrafting in solution or in solid form using a radical initiator. Thefree-radical induced grafting of ethylenically unsaturated carboxylicacid materials in solvents, such as benzene, is a preferred method. Itis carried out at an elevated temperature in the range of about 100° C.to 250° C., preferably 120° C. to 190° C. and more preferably at 150° C.to 180° C., e.g., about 160° C., in a solvent, preferably a minerallubricating oil solution containing, e.g., 1 to 50, preferably 5 to 30weight percent, based on the initial total oil solution, of the ethylenepolymer and preferably under an inert environment.

The free-radical initiators which may be used are peroxides,hydroperoxides, and azo compounds, and preferably those which have aboiling point greater than about 100° C. and decompose thermally withinthe grafting temperature range to provide free radicals. Representativeof these free-radical initiators are azobisisobutyronitrile and5-dimethyl-hex-3-yne -2,5 bis-tertiary-butyl peroxide. The initiator isused in an amount of between about 0.005% and about 1% by weight basedon the weight of the reaction mixture solution. The grafting ispreferably carried out in an inert atmosphere, such as under nitrogenblanketing. The resulting polymer intermediate is characterized byhaving carboxylic acid acylating functions within its structure.

In the solid or melt process for forming a graft polymer, theunsaturated carboxylic acid with the optional use of a radical initiatoris grafted on molten ethylene copolymer rubber using rubber masticatingor shearing equipment. The temperature of the molten material in thisprocess may range from about 150° C. to 400° C.

Polymer substrates or interpolymers are available commercially.Particularly useful are those containing from about 40 to about 60 molepercent ethylene units, about 60 to about 40 mole percent propyleneunits. Examples are "Ortholeum 2052" and "PL-1256" available from E. I.dupont de Nemours and Co. The former is a terpolymer containing about 48mole percent ethylene units, 48 mole percent propylene units and 4 molepercent 1,4-hexadiene units, having an inherent viscosity of 1.35. Thelatter is a similar polymer with an inherent viscosity of 1.95. Theviscosity average molecular weights of the two are on the order of200,000 and 280,000, respectively.

The polymer intermediate possessing carboxylic acid acylating functionsis reacted with an amino alkylthio thiadiazole compound represented bythe formula: ##STR2## in which R is --NH₂, --CH₂ --(CH₂)_(n) --NH₂,

--CH₂ --aryl-NH₂ in which n has a value from 1 to 10, and

R' is hydrogen, a hydrocarbyl radical having from 1 to 10 carbon atoms,or a hydroxyalkyl or alkoxyl radical having from 2 to 10 carbon atoms.

More particularly, R may be aminoethyl, aminopropyl, n may have a valuefrom 1 to 5 and the aryl radical has from 6 to 8 carbon atoms, and R'may be an alkyl radical having from 1 to 8 carbon atoms, an alkenylradical having from 5 to 12 carbon atoms or an aralkyl, alkaryl or arylradical having from 6 to 10 carbon atoms.

Particularly preferred amino-alkylthio thiazoles include2-amino-5-(ethylthio)-1,3,4-thiadiazole,2-amino-5-(methylthio)-1,3,4-thiadiazole, and 2-amino-5-(butylthio)-1,3,4-thiadiazole.

The reaction between the polymer substrate intermediate having graftedthereon carboxylic acid acylating function and the prescribed compoundis conducted by heating a solution of the polymer substrate under inertconditions and then adding the compound to the heated solution generallywith mixing to effect the reaction. It is convenient to employ an oilsolution of the polymer substrate heated to 140° C. to 175° C. whilemaintaining the solution under a nitrogen blanket. The compound is addedto this solution and the reaction is effected under the notedconditions.

The following examples illustrate the preparation of the polymerbackbone and the novel reaction product additive of the invention.

EXAMPLE I

Twenty grams of solid maleic anhydride grafted ethylene-propylenepolymer (rubber) in which the polymer substrate consisted of about 60mole percent ethylene and 40 mole percent propylene having an averagemolecular weight of 100,000 on which has been grafted 0.8 weight percentof maleic anhydride was dissolved in 145 grams of solvent neutral oil at160° C. with mechanical stirring while the mixture was maintained undera nitrogen blanket. After the rubber polymer had dissolved, mixing wascontinued for an additional hour at 160° C. 0.3 gram of neat2-amino-5-(ethylthio)-1,3,4-thiadiazole followed by 1.7 grams of lowmolecular weight ethylene oxide polymer was added to the oil solution ofthe polymer and a reaction effected over three hours at 160° C. undernitrogen. The reaction mixture containing the derivatized graft polymerwas then cooled and filtered. FTIR showed quantitative conversion.

EXAMPLE II

Thirty grams of solid maleic anhydride graft polymer (rubber) in whichthe polymer substrate consisted of about 60 mole percent ethylene and 40mole percent propylene having an average molecular weight of 100,000 onwhich had been grafted 0.8 weight percent of maleic anhydride wasdissolved in 191 grams of solvent neutral oil at 160° C. with mechanicalstirring while the mixture was maintained under a nitrogen blanket.After the rubber polymer had dissolved, mixing was continued for anadditional hour at 160° C. 0.47 gram of neat2-amino-5-(ethylthio)-1,3,4-thiadiazole followed by 9 grams of lowmolecular weight ethylene oxide polymer was added to the oil solution ofthe polymer and a reaction effected over three hours at 160° C. undernitrogen. The reaction mixture containing the derivatized graft polymerwas then cooled and filtered. FTIR showed quantitative conversion.

The novel graft and derivatized polymer of the invention is useful as anadditive for lubricating oils. They are multifunctional additives forlubricants being effective to provide dispersancy, antiwear properties,viscosity index improvement and antioxidant properties to lubricatingoils. They can be employed in a variety of oils of lubricating viscosityincluding natural and synthetic lubricating oils and mixtures thereof.The novel additives can be employed in crankcase lubricating oils forspark-ignited and compression-ignited internal combustion engines. Thecompositions can also be used in gas engines or turbines, automatictransmission fluids, gear lubricants, metal-working lubricants,hydraulic fluids, and other lubricating oil and grease compositions.

The base oil may be a natural oil including liquid petroleum oils andsolvent-treated or acid-treated mineral lubricating oils of theparaffinic, naphthenic and mixed paraffinic-naphthenic types.

In general, the lubricating oil composition of the invention willcontain the novel reaction product in a concentration ranging from about0.1 to 30 weight percent. A preferred concentration range for theadditive is from about 1 to 15 weight percent based on the total weightof the oil composition.

Oil concentrates of the additives may contain from about 1 to 50 weightpercent of the additive reaction product in a carrier or diluent oil oflubricating oil viscosity.

The novel reaction product of the invention may be employed in lubricantcompositions together with conventional lubricant additives. Suchadditives may include additional dispersants, detergents, antioxidants,pour point depressants, antiwear agents, and the like.

The novel additive reaction product of the invention was tested for itseffectiveness as a dispersant and as an antioxidant in a formulatedlubricating oil composition. In all of the examples, the polymersubstrate was similar, comprising about 58 mole percent ethylene, 42mole percent propylene having an average molecular weight of about80,000. The base lubricating oil used in the dispersancy test was atypical formulated lubricating oil having representative valuesillustrated in Table 1.

                  TABLE 1                                                         ______________________________________                                                           Parts by                                                                      Weight                                                     ______________________________________                                        Component                                                                     Solvent neutral oil A                                                                              75.25                                                    Solvent neutral oil B                                                                              21.64                                                    Zinc dialkyldithiophosphate                                                                        1.22                                                     4,4'Dinonyldiphenylamine                                                                           .39                                                      Overbased magnesium sulfonate                                                                      1.50                                                     Silicone antifoamant 150 ppm                                                  Product              10                                                       Analyses                                                                      Viscosity Kin, 40° C., CS                                                                   30.4                                                     Viscosity Kin, 100° C., CS                                                                  5.33                                                     Pour point, °F.                                                                             -10                                                      Ash Sulfated, %, D874                                                                              0.88                                                     Phosphorus, %, X-Ray 0.12                                                     Sulfur, %, X-Ray, Total                                                                            0.32                                                     Zinc, %, X-Ray       0.13                                                     ______________________________________                                    

Oil A had a sp. gr. 60°/60° F. of 0.858-0.868; Vis 100° F. 123-133; PourPoint 0° F. Oil B had a sp. gr. 60°/60° F. of 0.871-0.887; Vis. 100° F.325-350; Pour Point +10° F. Zinc salt is a salt of mixedalcohols-isopropanol and P₂ S₅ product as described in U.S. Pat. No.3,292,181. The overbased magnesium sulfonate had a TBN of 395 and is asalt of branched C₂₀ -C₄₀ monoalkylbenzene sulfuric acid (MW 530-540)together with about 10% magnesium carbonate, 14% magnesium hydroxide and4% magnesium sulfate.

The dispersant properties of the additive-containing oil are determinedin the Bench VE Dispersancy Test (BVET). Dispersancy of a lubricatingoil is determined relative to three references which are the resultsfrom three standard blends tested along with the unknown. The testadditives were blended into a formulated oil containing no dispersant.The additive reaction product was employed in the oil at a concentrationof 1.20 weight percent polymer solution. The numerical value of the testresults decreases with an increase in effectiveness.

                  TABLE 2                                                         ______________________________________                                        Bench VE Dispersancy Test                                                     Additive                Result                                                ______________________________________                                        Example I                67                                                   Example II               45                                                   Maleic anhydride grafted EPM                                                                          190                                                   Ethylene-Propylene Copolymer (EPM)                                                                    200                                                   ______________________________________                                    

The antioxidant properties of the novel reaction product in alubricating oil was determined in the Bench Oxidation Test. In thistest, 1.5 weight percent of the additive reaction product is blendedinto solvent neutral oil (S.U.S. at 100° F. of 130). The mixture iscontinuously stirred while being heated accompanied by bubbling withair. Samples are withdrawn periodically for analysis by DifferentialInfrared Absorption (DIR) to observe changes in the intensity of thecarboxyl vibration band at 1710 cm⁻¹. A low carboxyl vibration bandintensity indicates higher thermal-oxidative stability of the sample.

                  TABLE 3                                                         ______________________________________                                        Bench Oxidation Test                                                          Additive              Result                                                  ______________________________________                                        Example I             7                                                       Example II            8                                                       Maleic anhydride grafted (EPM)                                                                      13                                                      ______________________________________                                    

The test results for Examples I and II demonstrate substantialimprovements in antioxidant properties due to incorporation of the novelreaction product of the invention in an oil composition as compared tothe results obtained from known VI and dispersant VI improvers.

The antiwear properties of the novel reaction product in a lubricatingoil were determined in the 4-Ball Wear Test (4BWT) at two different testconditions. Antiwear of a lubricating oil was determined relative to onereference which is the result of an ethylene copolymer grafted withmaleic anhydride. The additive reaction product was employed in the oilat a concentration of 1.5 weight percent polymer solution. The numericalvalue of the test results decreases with an increase in effectiveness.

                  TABLE 4                                                         ______________________________________                                        4-Ball Wear Test                                                                             EPSA Polymer                                                                            Example II                                           ______________________________________                                        Avg. Scar Diameter mm                                                         Condition A      0.63        0.56                                             Condition B      0.51        0.46                                             ______________________________________                                         Condition A: 600 rpm, 40 kg, 200° F., 30 min., L689-4804.00 base       blend oil, Cumene hydroperoxide (80%) 1.7 wt %.                               Condition B: 1800 rpm, 40 kg, 200° F., 2 hr., L689-4804.00 base        blend oil.                                                               

The additive of Example II exhibited a substantial improvement in the4-Ball Wear Test under both test conditions in comparison to a maleicanhydride grafted ethylene-propylene copolymer.

What is claimed is:
 1. An additive reaction product prepared by thesteps comprising:(A) reacting a polymer prepared from ethylene and atleast one C₃ -C₁₀ alpha-monoolefin and, optionally, a polyene selectedfrom non-conjugated dienes and trienes comprising from about 15 to 80mole percent of ethylene, from about 20 to 85 mole percent of said C₃-C₁₀ alpha-monoolefin, and from about 0 to 15 mole percent of saidpolyene and having an average molecular weight ranging from about 5,000to 500,000 with at least one olefinic carboxylic acid acylating agent toform one or more acylating reaction intermediates characterized byhaving a carboxylic acid acylating function within their structure, and(B) reacting said reaction intermediate in (A) with an amino alkylthiothiadiazole represented by the formula: ##STR3## in which R is --NH₂,--CH₂ --(CH₂)_(n) --NH₂,--CH₂ --aryl--NH₂ in which n has a value from 1to 10, and R' is hydrogen, a hydrocarbyl radical having from 1 to 10carbon atoms, or a hydroxyalkyl or alkoxyl radical having from 2 to 10carbon atoms.
 2. A composition according to claim 1 in which saidpolymer has an average molecular weight from about 25,000 to 250,000. 3.A composition according to claim 1 in which said polymer has an averagemolecular weight from about 50,000 to 150,000.
 4. A compositionaccording to claim 1 in which said polymer comprises from about 25 to 75mole percent ethylene and from about 25 to 75 mole percent of a C₃ -C₈alpha-monoolefin.
 5. A composition according to claim 1 in which saidpolymer comprises from about 25 to 55 mole percent ethylene and fromabout 45 to 75 mole percent of propylene.
 6. A composition according toclaim 4 which contains from about 0.1 to 10 mole percent of a polyene.7. A composition according to claim 1 in which said olefinic carboxylicacid acylating agent is maleic anhydride.
 8. A composition according toclaim 1 in which said olefinic carboxylic acid acylating agent isitaconic anhydride.
 9. A lubricating oil composition comprising a majoramount of an oil of lubricating viscosity and a minor amount effectiveto impart viscosity index improvement, dispersancy, antiwear andantioxidant properties to said oil of an additive reaction productprepared by the steps comprising:(A) reacting a polymer prepared fromethylene and at least one C₃ -C₁₀ alpha-monoolefin and, optionally, apolyene selected from non-conjugated dienes and trienes comprising fromabout 15 to 80 mole percent of ethylene, from about 20 to 85 molepercent of said C₃ -C₂₀ alpha-monoolefin, and from about 0 to 15 molepercent of said polyene and having an average molecular weight rangingfrom about 5,000 to 500,000 with at least one olefinic carboxylic acidacylating agent to form one or more acylating reaction intermediatescharacterized by having a carboxylic acid acylating function withintheir structure, and (B) reacting said reaction intermediate in (A) withan amino alkylthio thiadiazole represented by the formula: ##STR4## inwhich R is --NH₂, --CH₂ --(CH₂)_(n) --NH₂,--CH₂ --aryl--NH₂ in which nhas a value from 1 to 10, and R' is hydrogen, a hydrocarbyl radicalhaving from 1 to 10 carbon atoms, or a hydroxyalkyl or alkoxyl radicalhaving from 2 to 10 carbon atoms.
 10. A lubricating oil compositionaccording to claim 9 containing from about 0.1 to 30.0 weight percent ofsaid additive based on the total weight of the oil composition.
 11. Alubricating oil composition according to claim 9 containing from about 1to 15.0 weight percent of said additive based on the total weight of theoil composition.
 12. A lubricating oil composition according to claim 9in which said polymer comprises from about 25 to 75 mole percentethylene and from about 25 to 75 mole percent of a C₃ -C₈alpha-monoolefin and has an average molecular weight ranging from about25,000 to 250,000.